1. Field of the Invention
This invention relates to frequency hopping kernels of wireless devices, and more particularly to a method and apparatus implementing an overlay adaptive frequency hopping kernel in a wireless communication system.
2. Description of Related Art
Wireless communication systems facilitate high-speed connectivity and data and voice transport from point-to-point and point-to-multipoint bases. Exemplary wireless communication systems include “Bluetooth™ 1 protocol” systems that facilitate the transport of data between Bluetooth™ devices such as wireless headsets, cellular phones and personal digital assistants (PDAs). The Bluetooth™ protocol is a global specification standard for radio communications operating at 2.4 GHz radio frequencies. Bluetooth™ devices (i.e., those that comply with the Bluetooth™ Specification) replace normal cable connections using short-range radio links. Bluetooth™ protocol technology is featured in cordless telephony, intercom, FAX and LAN access, and dial-up networking applications. Bluetooth™ wireless communication protocols are implemented in wireless headsets, cellular phones, PDAs, printers, and other mobile devices. Bluetooth™ devices are described in more detail in a specification produced by the Bluetooth™ special interest group (SIG), entitled “Bluetooth™ Specification Version 1.1”, electronically available to the public via the well-known Internet at <http://www.bluetooth.com>, published on Feb. 22, 2001, referred to herein as the “Bluetooth™ Specification”, and incorporated by reference herein in its entirety for its teachings on Bluetooth™ flow control, signals, devices and communication protocols and schemes. Bluetooth™ is a trademark of Bluetooth SIG, Inc.
Bluetooth™ devices typically communicate with other Bluetooth™ devices using either a “piconet” communication network topology or a “scatternet” communication network topology. Details regarding the Bluetooth™ communication protocols, piconet and scatternet communication networks are described in detail in the Bluetooth™ Specification. Specifically, the piconet networks are described in Section 1 of Part B of the Bluetooth™ Specification. The scatternet networks are described in Section 10.9 of Part B of the Bluetooth™ Specification.
A piconet is defined in the Bluetooth™ Specification as a communication system including two or more Bluetooth™ devices that share a common frequency hopping pattern and a common “Access Word” (or “access code”). Access codes are pre-defined bit patterns that are transmitted to a Bluetooth™ device at the beginning of “data packets.” Access codes are used to provide device synchronization and identification. As defined in detail in section 4.1 of the Bluetooth™ Specification, data is communicated between Bluetooth™ devices in the form of data packets. The data packets have a pre-determined format defined by the Bluetooth™ Specification. As defined therein, a data packet includes an “access code”, a “packet header” and a “payload” of data bits. Details regarding packets and access codes are described in more detail in Section 4.1–2 of the Bluetooth™ Specification.
At a minimum, a piconet comprises two or more Bluetooth™ devices, such as, for example, a portable PC and a cellular phone that communicate with each other via a piconet. A piconet can comprise a maximum of eight connected devices. When establishing a piconet, one and only one Bluetooth™ device acts as a master device. The master device initiates a connection to one or more slave devices. Any device in a piconet that is not a master device is, by definition, a slave device. Master-slave roles can be exchanged once a piconet is established. A master can become a slave, and a slave can become a master. Bluetooth™ master and slave devices utilize various Bluetooth™ protocols to exchange data.
Bluetooth™ wireless communication protocols aid in implementing various Bluetooth™ applications. Bluetooth™ applications utilize various links, or connections, to communicate between master and slave devices. As described in Part B, “Baseband Specification”, Sections 2.1 and 11, of the Bluetooth™ Specification, Bluetooth™ communication systems use a frequency hopping (FH) spread spectrum (FHSS) scheme (referred to hereinafter as the “Bluetooth™ FH kernel”) to communicate between master and slave devices. The term “frequency hopping spread spectrum scheme” refers to the well-known method of repeatedly switching channels or frequencies during data transmission. Frequency hopping spread spectrum schemes require channel switching or “hopping” to follow a specified algorithm so that devices can independently determine frequency-hopping (FH) sequences (i.e., ordered lists of frequencies).
Bluetooth™ communication protocols, as described in the aforementioned Part B, “Baseband Specification”, Section 2.1, of the Bluetooth™ Specification, determine FH sequences by using the Bluetooth™ device address and clock of a master device so that associated slave devices on a piconet can independently determine the pseudo-random FH sequences. Although an FH sequence associated with a master device is unique, piconets within close proximity can interfere with one another due to the Bluetooth™ protocol using only 79 independent channels. The Bluetooth™ FH kernel reduces collisions between nearby Bluetooth™ piconets due to properties of the pseudo-random sequence. Bluetooth™ communication protocols use the Bluetooth™ FH kernel, as described in the aforementioned Part B, “Baseband Specification”, Section 11, of the Bluetooth™ Specification, to select FH sequences and map FH sequences to hop frequencies.
Disadvantageously, the Bluetooth™ FH kernel selects hopping frequencies without regard to channel conditions, and thus, a hopping frequency having bad channel conditions (e.g., exhibiting small signal-to-noise ratios) caused by non-Bluetooth™ (FH) interferers can be selected. As is well known, transmitting data on frequencies with bad channel conditions increases the probability of the occurrence of reception errors. In any data communication system, it is desirable to reduce the occurrence of reception errors.
Therefore, a need exists for an adaptive frequency-hopping kernel that reduces reception errors in devices using frequency-hopping spread spectrum methods. Such a method should retain the pseudo-random properties of an original sequence. The method and apparatus should use channel conditions as an important criteria when determining frequency-hopping channels. The present invention provides such an adaptive frequency-hopping kernel.